Lately I've noticed quite a few answers that provide an answer to the O.P.'s question, but provide no supporting information.
Sometimes, comments are left, asking for more information; other times, these answers have been flagged by users, and the mod team has converted some of these answers into comments.
In at least one case, a user reacted quite negatively toward this, essentially saying, "I answered the O.P.'s question, didn't I? Why would I need to add something from a dictionary?"
Let me answer that here: Why? Because it's important that answers be accurate. Before you submit your answer, look at it with a critical eye, and ask yourself, "How would an O.P. (or anyone else visiting the site) know that my answer is correct? Are they just supposed to take my word for it?"
Note: I'm a native speaker; therefore, I know what I am talking about does not qualify as proof of correctness.
For example, suppose an O.P. asks:
The other day, a coworked asked if I had a Kleenex. I thought this was a strange question, because Kleenex is a specific brand of facial tissue. I keep a box of Puffs at my desk, and I assumed she didn't care what brand I gave her, but that got me wondering about brand names that have become so popular that we use those names to refer to the name of a product. (More examples I thought of include Band-Aids, Q-Tips, and Jello.) Is there a name for this phenomenon, when a brand name become synonymous with the product itself?
And I answer:
This is called a companym (a portmanteau word, from company and synonym).
Well, companym is indeed a nifty word, and I've answered the O.P.'s question. I might even get a few upvotes from people who think they've learned something new. Fact is, though, I'm full of baloney! There's no such word – at least, not outside my vocabulary of personally made-up portmanteaus.
Let's say someone else adds this answer:
These are called genericized trademarks.
What do you think? Codswallop again? As the old adage goes, "Fool me once, shame on you; fool me twice, shame on me!"
This is why answers are expected to have some sort of supporting information, which could be a link to a dictionary or Wikipedia article, or a few example usages, or even personal testimony of some sort.
When you do some research while composing an answer like this, not only will you strengthen the reliability of your answer, but you may improve its completeness as well:
These are called genericized trademarks. Wikipedia says that they are also referred to as proprietary eponyms, defining them as:
a trademark or brand name that has become the generic name for, or synonymous with, a general class of product or service
A separate Wikipedia entry has a list of examples, all the way from Astroturf to Zamboni. It includes two of those you mention in your question (Band-Aids and Q-Tips).
There are a few reasons someone might raise an eyebrow of doubt on a valid answer:
You've given an answer that's valid in American English, but not British English (or vice-versa). Without any supporting information, a whole continent of people might ask themselves, "Where did that come from?"
You've given a factual answer, but it's a lesser-used meaning of a word, and people who cross-check your answer in a dictionary may not find any listed definitions that support your assertion. It's a lot harder to question the accuracy of an answer when you've provided examples from authoritative sources that back you up!
If you think substantiating an answer in this manner is too much trouble, then I would recommend just leaving a comment instead. As a community, we're not just trying to answer questions, but we are striving to supply reliable answers.